U.S. Frost Dates by Weather Station

NOAA station USC00105980 · Idaho

Frost Dates for Minidoka Dam, ID

NOAA weather station Minidoka Dam (USC00105980), Idaho · elevation 4164 ft (1269 m) · hardiness zone 6a*

  • Lower-risk planting dateafter June 5only 1 spring in 10 still has a frost later
  • Typical last frostMay 1650% chance of a frost after it
  • Typical first fall frostOctober 150% chance of a frost before it
  • Frost-free season136 daystypical year, 32°F
  • Hardiness zone6acalculated*

The year at a glance

Frost season at Minidoka Dam, IDSpring: a frost after April 30 in 9 years out of 10, after May 16 in half of the years, after June 5 in 1 year out of 10. Fall: the first frost comes before September 13 in 1 year out of 10, before October 1 in half of the years, before October 16 in 9 years out of 10. Typical frost-free season: 136 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 16First frost ~Oct 1Frost season at Minidoka Dam, IDSpring: a frost after April 30 in 9 years out of 10, after May 16 in half of the years, after June 5 in 1 year out of 10. Fall: the first frost comes before September 13 in 1 year out of 10, before October 1 in half of the years, before October 16 in 9 years out of 10. Typical frost-free season: 136 days.JFMAMJJASONDLast frost ~May 16First frost ~Oct 1
frost likely chance fading 90% → 10% frost-free in a typical yearThe year at a glance. Blue: frost is likely; the gradient fades as the chance drops from 90% to 10%; green: the frost-free part of a typical year.

Frost dates (32°F)

Probability of frost, based on 26 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)June 5September 13
50% (typical)May 16October 1
90% (likely)April 30October 16
Frost-free season (32°F, 50% chance)
136 days
Hard frost (28°F), last in spring, 50% chance after
May 2
Hard frost (28°F), first in fall, 50% chance before
October 15

The last 15 years (2006–2020 normals)

Typical last frost May 19 (3 days later than the 30-year normal), typical first fall frost October 1. Frost-free season 132 days.

A shorter, more recent NOAA period. The 30-year normals above remain the main reference: 15 years carry more year-to-year noise.

Add these dates to your calendar Yearly reminders for the typical last frost, the lower-risk planting date and the typical first fall frost (.ics).

How the chance of frost changes with the date

Spring at Minidoka Dam: chance of a frost after this dateSpring, chance of a frost after the date: 10% June 5, 20% May 30, 30% May 24, 40% May 20, 50% May 16, 60% May 13, 70% May 9, 80% May 5, 90% April 30. Observed last spring frost in recent years: 2021 May 12, 2022 May 24, 2023 April 28, 2024 June 18, 2025 April 29.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1Jun 5May 16Apr 302021: May 122022: May 242023: April 282024: June 182025: April 29Fall at Minidoka Dam: chance of a frost before this dateFall, chance of a frost before the date: 10% September 13, 20% September 20, 30% September 24, 40% September 28, 50% October 1, 60% October 3, 70% October 6, 80% October 11, 90% October 16. Observed first fall frost in recent years: 2021 September 26, 2022 October 14, 2023 October 26, 2024 October 1, 2025 October 17.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Nov 1Sep 13Oct 1Oct 162021: September 262022: October 142023: October 262024: October 12025: October 17
Two charts, because spring and fall answer different questions: in spring, the chance that a frost still comes after a date; in fall, the chance that the first frost has already come before it. NOAA publishes these odds from 10% to 90%, so the lines stop there. ◆ marks the actual date in each recent year.

What actually happened in recent years

Observed dates of the last spring and first fall frost (32°F) at this station; ◆ marks them on the charts above
YearLast spring frostFirst fall frost
2021May 12September 26
2022May 24October 14
2023April 28October 26
2024June 18October 1
2025April 29October 17
2026incomplete recordseason not over yet

What these dates mean

The 136 days between the 50% dates in Minidoka Dam—May 16 in spring and October 1 in fall—mark the interval during which a light frost (32 °F) is less likely than not, giving gardeners a window for tender crops.

In this location a cautious spring plan would wait until June 5, when there is only a 10 % chance of a frost later, before setting out tender crops, while a cautious fall plan would aim to finish harvesting by September 13, when there is only a 10 % chance that a frost has arrived earlier. By contrast, planting on April 30 or keeping crops out until October 16 carries a 90 % chance of frost and is a gamble.

Hard-frost dates—May 2 and October 15—are noted because a temperature of 28 °F can injure or kill plants that survive a light frost at 32 °F.

How to read the probabilities

The dates are probabilities from 30 years of weather, not a forecast for this year.

  • Spring: "10% after June 5" means that in about one spring out of ten a frost still happens after that date. The 90% date is the earliest: a frost after it happens in most years.
  • Fall: "10% before September 13" means that in about one fall out of ten the first frost arrives before that date.
  • 50% is the typical date: half of the years are earlier, half are later.
  • A light frost (32°F) damages tender plants; a hard frost (28°F) also stops most hardy vegetables.

Nearby weather stations

Map of weather stations near Minidoka Dam, IDNumbered nearest stations: 1 — Paul, ID — 14 mi; 2 — Burley, ID — 16 mi; 3 — Hazelton, ID — 33 mi; 4 — Oakley, ID — 37 mi; 5 — Richfield, ID — 42 mi.UT25 mi · 40 km1. Paul, ID — 14 mi12. Burley, ID — 16 mi23. Hazelton, ID — 33 mi34. Oakley, ID — 37 mi45. Richfield, ID — 42 mi5
  1. Paul, ID 14 mi (23 km)
  2. Burley, ID 16 mi (26 km)
  3. Hazelton, ID 33 mi (53 km)
  4. Oakley, ID 37 mi (59 km)
  5. Richfield, ID 42 mi (68 km)

Sources

* Hardiness zone 6a: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 42.6769, -113.5022.